MR. LUBBOCK ON THE TIDES. 
53 
The agreement so far between theory and observation is not less remarkable 
than that at the London Docks which I have before noticed, (see Phil. Trans. 
1831 , p. 388 ). The irregularities in the errors given in the fourth column arise 
from the paucity of the observations employed. 
As it would be of great importance to predict, if possible, any remarkably 
high tides which might take place, in order that precautions might be taken 
to avoid any disastrous consequences, I requested M. Dessiou to calculate, 
from the Tables in the Companion to the British Almanac * for 1831 , the times 
and heights of high water at the London Docks corresponding to some remark- 
ably high tides which have been observed, in order to see how nearly those 
Tables can be depended upon in extreme cases. 
The following Table exhibits the results he obtained. 
Time of High Water. 
Height of High Water. 
Direction 
of the 
Wind. 
Observed. 
Calculated. 
Observed. 
Calculated. 
h m 
h m 
ft. in. 
ft. in. 
1812. Oct. 21. 
2 0 A.M. 
2 10 A.M. 
25 1 
23 7 \ 
NW 
2 10 p.m. 
2 30 P.M. 
25 8 
23 10 
NW 
1821. Dec. 28. 
3 45 a.m. 
4 10 A.M. 
23 10 
22 9| 
SE 
4 15 p.m. 
4 29 p.m. 
25 10 
22 8| 
ESE 
1824. Dec. 23. 
3 10 A.M. 
3 28 a.m. 
25 11 
22 5§ 
NW 
3 40 p.m. 
3 46 p.m. 
23 6 
22 5| 
S 
1827- Oct. 23. 
11 45 p.m. 
0 5 A.M.f 
26 0 
21 6± 
NW 
Nov. 1. 
0 10 P.M. 
0 25 p.m. 
22 3 
21 8| 
NW 
These results are extremely unsatisfactory ; and I fear that it will happen 
sometimes, although but rarely, that a considerable error will occur in the cal- 
culated times and heights of high water, owing no doubt to gales of wind in the 
Channel or North Sea, or even perhaps in the Atlantic. The average error in 
using the Tables of the Companion, as M. Dessiou found by his calculations 
for the year 1826 , (see Phil. Trans. 1831 , p. 381 ,) in the time of high water is 
about 12 m , and in the height about 8 inches ; this error however is more I be- 
* In using these Tables the moon’s transit should be equated or reduced to mean time before the 
corrections are applied. The example given in the Companion is thei'efore incorrect, 
f November 1. 
